U.S. patent number 8,717,694 [Application Number 13/330,461] was granted by the patent office on 2014-05-06 for identifying defective slots in a disk drive tester.
This patent grant is currently assigned to Western Digital Technologies, Inc.. The grantee listed for this patent is Rokhaizam Bin Mohd Ali, Hon Kong Liew, Minh N. Trinh. Invention is credited to Rokhaizam Bin Mohd Ali, Hon Kong Liew, Minh N. Trinh.
United States Patent |
8,717,694 |
Liew , et al. |
May 6, 2014 |
Identifying defective slots in a disk drive tester
Abstract
A disk drive tester is disclosed operable to test a plurality of
disk drives, each disk drive comprising a head actuated over a
disk. The disk drive tester comprises a plurality of test slots,
where each test slot is operable to receive one of the disk drives.
The disk drive tester further comprises an interface for receiving
vibration data from the disk drives, wherein the vibration data at
least partially represents a vibration applied to each disk drive
by the respective test slot. The disk drive tester further
comprises control circuitry operable to detect when one of the test
slots is defective in response to the vibration data.
Inventors: |
Liew; Hon Kong (Bukit Rimau,
MY), Ali; Rokhaizam Bin Mohd (Shah Alam,
MY), Trinh; Minh N. (Irvine, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Liew; Hon Kong
Ali; Rokhaizam Bin Mohd
Trinh; Minh N. |
Bukit Rimau
Shah Alam
Irvine |
N/A
N/A
CA |
MY
MY
US |
|
|
Assignee: |
Western Digital Technologies,
Inc. (Irvine, CA)
|
Family
ID: |
50552833 |
Appl.
No.: |
13/330,461 |
Filed: |
December 19, 2011 |
Current U.S.
Class: |
360/31;
702/56 |
Current CPC
Class: |
G11B
19/048 (20130101); G11B 5/455 (20130101); G11B
5/59694 (20130101); G11B 5/5582 (20130101); G11B
5/59627 (20130101) |
Current International
Class: |
G11B
27/36 (20060101); G01F 23/00 (20060101); G01L
7/00 (20060101); G01N 11/00 (20060101); G01F
17/00 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Holder; Regina N
Claims
What is claimed is:
1. A disk drive tester operable to test a plurality of disk drives,
each disk drive comprising a head actuated over a disk, the disk
drive tester comprising: a plurality of test slots, where each test
slot is operable to receive one of the disk drives; an interface
for receiving vibration data from the disk drives, wherein the
vibration data at least partially represents a vibration applied to
each disk drive by the respective test slot; and control circuitry
operable to: execute at least one test on each disk drive; and
detect when one of the test slots is defective in response to the
vibration data.
2. The disk drive tester as recited in claim 1, wherein the control
circuitry is further operable to: generate a baseline for the
vibration data by testing a plurality of the disk drives, wherein
the baseline represents a nominal test condition; and detect when
one of the test slots is defective in response to the baseline and
vibration data received after generating the baseline.
3. The disk drive tester as recited in claim 2, wherein the control
circuitry is operable to detect when one of the test slots is
defective when the corresponding vibration data received from a
plurality of the disk drives deviates from the baseline by a
threshold.
4. The disk drive tester as recited in claim 1, wherein the control
circuitry is operable to detect when one of the test slots is
defective when a running average of the corresponding vibration
data received from a plurality of the disk drives exceeds a
threshold.
5. The disk drive tester as recited in claim 4, wherein the control
circuitry is operable to: generate a baseline for the vibration
data by testing a plurality of the disk drives, wherein the
baseline represents a nominal test condition; and configure the
threshold in response to the baseline.
6. The disk drive tester as recited in claim 1, wherein the
vibration data comprises a non-repeatable runout (NRRO) of the head
while tracking a substantially circular track on the disk.
7. The disk drive tester as recited in claim 6, wherein the control
circuitry is operable to detect when one of the test slots is
defective when the NRRO of a plurality of consecutive disk drives
tested by the test slot exceeds a threshold.
8. The disk drive tester as recited in claim 7, wherein the control
circuitry is operable to: generate a baseline for the vibration
data by testing a plurality of the disk drives, wherein the
baseline represents a nominal test condition; and configure the
threshold in response to the baseline.
9. A method of operating a disk drive tester for testing a disk
drive, the disk drive comprising a head actuated over a disk, the
method comprising: inserting a disk drive into a test slot;
executing at least one test on the disk drive; receiving vibration
data from the disk drive, wherein the vibration data at least
partially represents a vibration applied to the disk drive by the
test slot; and detecting the test slot is defective in response to
the vibration data.
10. The method as recited in claim 9, further comprising:
generating a baseline for the vibration data by testing a plurality
of disk drives, wherein the baseline represents a nominal test
condition; and detecting when the test slot is defective in
response to the baseline and vibration data received after
generating the baseline.
11. The method as recited in claim 10, further comprising detecting
when the test slots is defective when the vibration data deviates
from the baseline by a threshold.
12. The method as recited in claim 9, further comprising detecting
when the test slot is defective when a running average of the
vibration data exceeds a threshold.
13. The method as recited in claim 12, further comprising:
generating a baseline for the vibration data by testing a plurality
of the disk drives, wherein the baseline represents a nominal test
condition; and configuring the threshold in response to the
baseline.
14. The method as recited in claim 9, wherein the vibration data
comprises a non-repeatable runout (NRRO) of the head while tracking
a substantially circular track on the disk.
15. The method as recited in claim 14, further comprising detecting
when one of the test slots is defective when the NRRO of a
plurality of consecutive disk drives tested by the test slot
exceeds a threshold.
16. The method as recited in claim 15, further comprising:
generating a baseline for the vibration data by testing a plurality
of disk drives, wherein the baseline represents a nominal test
condition; and configuring the threshold in response to the
baseline.
Description
BACKGROUND
Disk drives are employed in numerous applications such as computer
systems (e.g., desktops, laptops, portables, etc.) and consumer
devices (e.g., music players, cell phones, cameras, etc.). A disk
drive manufacturer will typically perform a number of production
line tests to detect problems prior to shipping. For example, a
defect scan may be preformed on each disk drive in order to detect
and map out defective sectors or tracks, or various components may
be tested, such as testing the heads to determine whether they
should be depopulated or replaced. The disk drive may also maintain
a number of logs, such as a manufacture log that stores
manufacturing data of the disk drive, or a Self-Monitoring,
Analysis, and Reporting Technology (S.M.A.R.T.) log that stores
diagnostic information used for failure prediction while deployed
in the field.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A shows a disk drive comprising a head actuated over a disk
according to an embodiment of the present invention.
FIG. 1B shows a disk drive tester comprising a plurality of test
slots according to an embodiment of the present invention.
FIG. 1C is a flow diagram according to an embodiment of the present
invention wherein a defective test slot is detected in response to
vibration data generated by the disk drives.
FIG. 2 is a flow diagram according to an embodiment of the present
invention wherein a defective test slot is detected relative to a
baseline generated while testing a plurality of disk drives under a
nominal test condition.
FIG. 3A shows a distribution of a vibration amplitude received from
a plurality of disk drives inserted into a plurality of the test
slots.
FIG. 3B illustrates a distribution of a vibration amplitude
received from a defective test slot.
FIG. 3C illustrates an embodiment of the present invention wherein
a defective test slot is detected when a sliding window average of
the vibration amplitude exceeds a threshold configured from the
baseline.
FIG. 4 shows an embodiment of the present invention wherein the
vibration data comprises a non-repeatable runout (NRRO) measured by
each disk drive while tracking a substantially circular track on
the disk.
FIG. 5 is a flow diagram according to an embodiment of the present
invention wherein a defective test slot is detected when N
consecutive disk drives generate a NRRO exceeding a baseline
threshold.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
FIG. 1B shows a disk drive tester 2 according to an embodiment of
the present invention operable to test a plurality of disk drives.
As shown in FIG. 1A, each disk drive 4.sub.i comprises a head 6
actuated over a disk 8. The disk drive tester 2 comprises a
plurality of test slots, where each test slot is operable to
receive one of the disk drives 4.sub.i. The disk drive tester 2
comprises an interface for receiving vibration data from the disk
drives 4.sub.i, wherein the vibration data at least partially
represents a vibration applied to each disk drive 4, by the
respective test slot. The disk drive tester further comprises
control circuitry (e.g., a computer 10) operable to execute the
flow diagram of FIG. 1C, wherein vibration data is received from
the disk drives (step 12) and a test slot is detected as defective
(step 16) in response to the vibration data (step 14).
In the embodiment of FIG. 1A, the disk 8 comprises a plurality of
servo sectors 18.sub.0-18.sub.N recorded around the circumference
of the disk 8. Each servo sector 18 comprises position information,
such as a track address and servo bursts that define a plurality of
concentric servo tracks 20. Control circuitry 22 within the disk
drive 4, processes a read signal 24 emanating from the head 6 to
demodulate the servo sectors 18.sub.0-18.sub.N into a position
error signal (PES) representing a position error of the head 6
relative to a target servo track. The control circuitry 22 filters
the PES using a suitable compensation filter to generate a control
signal 26 applied to a voice coil motor (VCM) 28 that rotates an
actuator arm 30 about a pivot in order to actuate the head 6 over
the disk 8 in a direction that reduces the PES. In an embodiment
described below, the control circuitry 22 may generate the
vibration data based on the PES while attempting to track one of
the servo tracks (e.g., generating the vibration data by extracting
a non-repeatable runout (NRRO) from the PES).
FIG. 2 is a flow diagram according to an embodiment of the present
invention that expands on the flow diagram of FIG. 1C. As the disk
drives are inserted into the test slots (step 32) and the vibration
data is received from the disk drives (step 34), the vibration data
is saved in a database (step 36). This processes is repeated (step
38) until a sufficient number of disk drives have been processed to
establish a baseline that represents a nominal test condition. The
vibration data received thereafter is compared to the baseline in
order to detect a defective test slot (step 40).
Any suitable baseline may be generated based on the vibration data
received from a plurality of disk drives tested by a plurality of
the test slots. FIG. 3A shows a distribution for a vibration
amplitude received from a plurality of the disk drives tested by a
plurality of the test slots. In one embodiment, a distribution for
the vibration amplitude may be generated for each test slot,
wherein each sample point in the distribution represents the
vibration amplitude for one of the disk drives tested. The
distribution for a plurality of the test slots may then be averaged
to generate a nominal distribution presenting a nominal test slot
as illustrated in FIG. 3A.
FIG. 3B illustrates an embodiment of the present invention wherein
a defective test slot will generate an abnormal distribution for
the vibration amplitudes received from the tested disk drives. The
distribution is abnormal relative to the baseline distribution. Any
statistical data point may be evaluated to detect a defective test
slot, wherein in an embodiment illustrated in FIG. 3C, a defective
test slot may be detected when the average vibration amplitude
exceeds the baseline average amplitude (FIG. 3A) plus a margin. In
one embodiment, a sliding window average of the vibration amplitude
is compared to the threshold in order to filter outliers while
quickly detecting a test slot that may be degrading over time as
illustrated in FIG. 3C.
The disk drive tester 2 of FIG. 1B may receive any suitable
vibration data from each disk drive. FIG. 4 shows an embodiment of
the present invention wherein the vibration data comprises a
non-repeatable runout (NRRO) of the head while tracking a
substantially circular track on the disk (e.g., a servo track 20 of
FIG. 1A). In one embodiment, the NRRO is extracted from the PES
generated by the disk drive servo system. In one embodiment, the
NRRO represents the degree of randomness in the PES, which may be
measured in any suitable manner, such as using any suitable signal
processing algorithm (e.g., Fourier transform). In one embodiment,
the NRRO may be measured by compensating for a repeatable runout
(RRO) using feed-forward compensation, wherein the residual PES
after feed-forward compensation represents the NRRO. In one
embodiment, the disk drive may return the average NRRO for the
entire servo track to the disk drive tester, and in another
embodiment, the disk drive may return the NRRO for each servo
sector in the servo track (e.g., residual PES at each servo
sector).
FIG. 5 shows a flow diagram according to an embodiment of the
present invention wherein disk drives are inserted into the test
slots (step 42) and the NRRO is received from the disk drives (step
44) which is saved in a database (step 46). This process is
repeated (step 48) until enough disk drives have been processed to
generate a baseline. A threshold is then selected for the NRRO data
based on the baseline (step 50). Thereafter when disk drives are
inserted into the test slots (step 52) and the NRRO received from
each disk drive (step 54), the NRRO is compared to the threshold
(step 56). When the NRRO for N consecutive disk drives tested by
one of the test slots exceeds the threshold (step 58), the test
slot is detected as defective (step 60). Requiring N consecutive
disk drives to generate a NRRO that exceeds the threshold before
detecting a defective test slot is a form of filtering the NRRO to
ensure the test slot is truly defective.
Other forms of vibration data that may be employed instead of, or
in addition to, the NRRO data may include vibration data generated
from a suitable vibration sensor, such as a suitable piezoelectric
shock sensor or accelerometer. In another embodiment, the vibration
data may include fly height data for the head, wherein a vertical
vibration applied to the disk drive may be reflected in the fly
height data. The fly height data may be generated in any suitable
manner, such as by monitoring the read signal amplitude (or read
signal amplifier) which may fluctuate as the fly height changes. In
another embodiment, the head may include a suitable fly height
sensor, such as a tunneling sensor, capable of generating a direct
measurement of the fly height.
In one embodiment, when a test slot is detected as defective, the
disk drive tester may disable the test slot to prevent it from
being used to test subsequent disk drives. In this manner, the disk
drive tester can continue testing disk drives using the good test
slots rather than take the disk drive tester off-line for repairs.
When the number of failing test slots exceeds a threshold, the disk
drive tester may be taken off-line for repairs so that the
throughput can be increased.
The disk drive tester 2 of FIG. 1B may comprise any suitable
circuitry for implementing the flow diagrams disclosed herein. In
one embodiment, the control circuitry comprises a microprocessor
operable to execute code segments of a computer program stored on
any suitable computer readable storage medium (e.g., a disk or
semiconductor memory). In the embodiment of FIG. 1B, the disk drive
tester 2 comprises a computer 10 including a monitor and keyboard
to facilitate a user interfacing with the disk drive tester through
a graphical user interface (GUI). The computer 10 in FIG. 1B may be
connected directly to the disk drive tester 2 using a suitable
cable (e.g., a Universal Serial Bus (USB) cable), or the computer
10 may be connected to the disk drive tester 2 over a local area or
wide area network (i.e., the computer 10 may be at a remote
location and access the disk drive tester 2 over a network). In
another embodiment, the disk drive tester may comprise an
integrated computer and a user interface in the form of a control
panel. In yet another embodiment, the disk drive tester may
communicate with a computer (e.g., a server) over a network. For
example, a server may be used to monitor a number of the disk drive
testers and notify an end user when a disk drive tester requires
servicing. In one embodiment, an end user may insert the disk
drives into and remove the disk drives from the test slots of the
disk drive tester, and in another embodiment each disk drive may be
inserted into and removed from the test slots using a suitable
robotic system.
* * * * *